1. Field of the Invention
The present invention relates to an edge-type backlight unit, more particularly, which has a plurality of arrays of red, blue and green LEDs to provide a light source.
2. Description of the Related Art
Development in the electronic device industry also has led to development in various kinds of small-sized display devices consuming less power, and image devices, computers, mobile telecommunication terminals using such display devices. A liquid crystal display (LCD) has emerged in line with this trend and drawn attention as a display device for monitors and mobile telecommunication terminals.
A liquid crystal panel of the LCD does not generate light on its own. Thus, typically the liquid crystal panel is equipped with a backlight unit including a light source for backlighting the liquid crystal panel and a light guide plate.
A cold cathode fluorescent lamp (CCFL) has been conventionally utilized as a light source of an LCD backlight. The CCFL may trigger environmental pollution due to use of a mercury gas. Also, the CCFL is low in response rate and color reproducibility, and inadequate for reducing the weight and size of the LCD panel.
In contrast, a light emitting diode (LED) is environment-friendly and can respond fast with several nano seconds, thus effective in video signal stream. Moreover, the LED can be impulsively driven, reproduce colors by 100% or more and arbitrarily change brightness and color temperature by adjusting a light amount of red, green and blue LEDs. Also, the LED carries advantages leading to a lighter weight and smaller sized LCD panel. Thus the LED is actively adopted as a backlight source of the LCD panel.
In general, the LCD backlight employing the LEDs includes an edge-type backlight and a direct-type backlight depending on location of a light source. In the former, a light source is shaped as an elongated bar and disposed at a side of a light guide plate to irradiate light onto the LCD panel. In the latter, a surface light source is substantially identical in size to the LCD panel and disposed under the LCD panel to directly irradiate light onto the LCD panel.
FIG. 1 is a schematic view illustrating a conventional edge-type backlight unit 100 using a light emitting diode and a light source 110. As shown in FIG. 1, the edge-type backlight unit 100 includes a light guide plate 121 having a light incidence part 121 formed on a side surface thereof and the light source 110 including light emitting diodes (LED)s 112 arrayed in rows on a board 111.
The LEDs 112 are arrayed in rows on the board 111 in an order of red-green-blue to irradiate light onto the light incidence part 121 of the light guide plate 130. Light emitted from the rows of the red, green and blue LEDs 112 enters the light incidence part 121 of the light guide plate 120 to be combined together into white light. The white light is supplied to a liquid crystal panel (not illustrated) disposed over the light guide plate 120.
However, the conventional LED arrangements require high-power LED chips to produce white light. These LED chips greatly differ in emission light, thereby not forming uniform white light on an overall LCD screen. This accordingly causes partial color stains. Also, the conventional LED arrangements result in color stains due to imperfect light mixture in the liquid crystal panel in the vicinity of the LEDs, thereby degrading an overall image quality of the LCD device.
In addition, a reflective film of the light guide plate should be patterned more elaborately to reduce such color stains.